The invention relates to heat exchangers and method of their manufacture and more particularly to heat exchangers for cooling electrical devices in which heat is removed by a metallic element by conduction and transferred to a moving gas stream by presentation of a large surface area of the metallic element to the gas stream.
Electrical devices often produce heat as an unwanted byproduct of their operation. The heat must be removed from the apparatus to prevent elevation of the temperature to undesirable levels. In some cases, air is blown directly over the heat producing elements. When this is ineffective or undersirable, special heat exchangers may be used for more effective transfer of the heat.
These may take the form of a metal heat sink to which the heat producing element is thermally coupled. The heat sink or exchanger may have a flat surface for coupling to a flat surface of the element. Often a heat-conducting paste between the two surfaces ensures good heat transfer. The exchanger is provided with a large surface area exposed to the cooling air. This large surface may be in the form of ridges, fins and the like. The cooling air may be moved by simple convection, however it is more common to force air by a fan or blower. The preferred, compact and inexpensive blowers for this purpose are the pancake type of fans as exemplified by: Model 148VK-0282 manufactured by ETRI INC., Monroe, N.C.
They move considerable volumes of air, but only at low pressure. They will not operate effectively into a high resistance to air flow. Many of the heat exchangers of the prior art present a large surface area but offer so much resistance to air flow that they cannot be used with a pancake fan. Furthermore, it is expensive to manufacture a low resistance heat exchanger with a large heat transfer capability.